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Flexible pipes for production of oil and gas typically present a corrugated inner surface. This has been identified as the cause of "singing risers": Flow-Induced Pulsations due to the interaction of sound waves with the shear layers at the small cavities present at each of the multiple corrugations. The new flexible technology discussed in this paper, called K-carcass, is made of shaped wires and presents a very different bore profile compared to other folded-strip flexibles. In a preliminary study based on small scale testing, it was showed that the new inner profile geometry of this technology was more robust for Flow-Induced Pulsations compared to the folded strip carcass. A qualification program was initiated to address the different risks associated with the introduction of a new pipe technology. A primary goals of this qualification program was to extend the results of the preliminary study to the actual carcass at field conditions (natural gas at production pressure). In this paper, the method followed to qualify the singing behavior of the new flexible technology as installed in the field at operational conditions is considered. The testing program and the scaling approach used to extrapolate results obtained at different scales towards full-scale pipes are described. The program includes a combination of small-scale and large-scale testing. The small scale singing testing consists of blow-through tests of 2" and 3" pipes with corrugated inner bore with air at low pressures on a setup with well-defined acoustic boundary conditions. The large-scale singing testing consists of similar tests on 3" and 5" pipes with natural gas at close-to-operational pressures. These tests are completed with full-scale tests, where a reference riser and a prototype of new-technology riser are tested with natural gas at high pressure. The combination of scales and gas properties at which the tests are done, and the continuity between the different tests conditions, will allow the validation of theoretical and empirical scaling laws used in the qualification of the new riser in operational conditions. The blow-through tests with the prototype pipe with the new K-carcass tested with natural gas at close-to-operational pressure did not show any singing. In contrast, the reference pipe (with folded-strip carcass) started singing even at low velocities. The test results can be extended to an allowable production envelope for a pipe in field conditions. Such a qualification of new technology has to rely on existing prediction tools. As these tools were developed to analyze the singing behavior of the existing technologies, this combined theoretical and experimental approach reduces the risks associated with the introduction of a new technology.
Flexible pipes for production of oil and gas typically present a corrugated inner surface. This has been identified as the cause of "singing risers": Flow-Induced Pulsations due to the interaction of sound waves with the shear layers at the small cavities present at each of the multiple corrugations. The new flexible technology discussed in this paper, called K-carcass, is made of shaped wires and presents a very different bore profile compared to other folded-strip flexibles. In a preliminary study based on small scale testing, it was showed that the new inner profile geometry of this technology was more robust for Flow-Induced Pulsations compared to the folded strip carcass. A qualification program was initiated to address the different risks associated with the introduction of a new pipe technology. A primary goals of this qualification program was to extend the results of the preliminary study to the actual carcass at field conditions (natural gas at production pressure). In this paper, the method followed to qualify the singing behavior of the new flexible technology as installed in the field at operational conditions is considered. The testing program and the scaling approach used to extrapolate results obtained at different scales towards full-scale pipes are described. The program includes a combination of small-scale and large-scale testing. The small scale singing testing consists of blow-through tests of 2" and 3" pipes with corrugated inner bore with air at low pressures on a setup with well-defined acoustic boundary conditions. The large-scale singing testing consists of similar tests on 3" and 5" pipes with natural gas at close-to-operational pressures. These tests are completed with full-scale tests, where a reference riser and a prototype of new-technology riser are tested with natural gas at high pressure. The combination of scales and gas properties at which the tests are done, and the continuity between the different tests conditions, will allow the validation of theoretical and empirical scaling laws used in the qualification of the new riser in operational conditions. The blow-through tests with the prototype pipe with the new K-carcass tested with natural gas at close-to-operational pressure did not show any singing. In contrast, the reference pipe (with folded-strip carcass) started singing even at low velocities. The test results can be extended to an allowable production envelope for a pipe in field conditions. Such a qualification of new technology has to rely on existing prediction tools. As these tools were developed to analyze the singing behavior of the existing technologies, this combined theoretical and experimental approach reduces the risks associated with the introduction of a new technology.
Large gas field developments are an important trend of the oil and gas industry and is likely to be reinforced in the next decades. For these developments, flexible pipes with larger Inner Diameter (ID) and high flow rates are more and more required. This paper presents solutions developed to improve flow assurance in gas flexible pipes by assessing and removing flow induced pulsations (FLIP) risk occurrence and optimizing the maximum allowable flow rate. This trend leads the industry to have a kind interest in FLIP free flowlines and risers as well as in flexible pipes with improved flow rates capacities for equivalent diameters. Beginning of the 2000’s smooth bore gas export flexible riser was a pioneered FLIP free solution which is now a well-known, field proven and recognized technology. In addition, the market and industry trend have led to develop a full panel of solutions to answer new market requirements: FLIP and pressure losses methodologies, appropriate selection of conventional carcass and smooth bore flexible pipes (smooth carcass & plastic smooth bore). This paper describes the different solutions to enhance the flow assurance of flexible pipes for gas applications (less pressure losses & FLIP proof) with different flexible pipes solutions. Then a focus is done on the development of a cost-effective solution applicable to all types of pipes: the smooth carcass. This new carcass is an incremental improvement of existing technology. The industrialization, prototype manufacturing, qualification program and technical performances obtained so far including FLIP aspect, pressure loss and global mechanical behavior are detailed. Results have demonstrated that the smooth carcass allows reducing the pressure losses compared to flexible pipe with standard carcasses and thus to optimize the fluids flow rates or to reduce the flexible pipe internal diameters. Complete API 17J qualification compliance is planned for end 2018 for both static and dynamic applications. Specific dedicated competencies and technologies were developed to answer market requirements of the new gas field developments. Furthermore, the development of smooth carcass will tackle the singing phenomenon on gas flexible lines, and provide an optimized solution for flow assurance improvement to oil and gas operators.
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